Cellulose base lubricating grease



Patented June 29, 1954 CELLULOSE BASE LUBRICATING GREASE Aurelio F.Sirianni and Ira E. Puddington, t-

tawa, Ontario, Canada, assignors to National Research Council, Ottawa,Ontario, Canada, a

body corporate No Drawing. Application October 17, 1951, Serial No.251,818

9 Claims. 1

The present invention relates to cellulose base lubricating grease, thatis, lubricating grease wherein cellulose, or cellulose derivatives, areemployed as the thickening or gel forming material which forms thegrease structure.

The present application is a continuation-inpart of our copendingapplications, Serial No. 66,130 and Serial No. 66,133, filed December18, 1948, now Patents No. 2,583,603 and 2,583,606, issued January 29,1952.

In the above-mentioned applications, lubricating greases and processesfor their preparation are described where the normal solvent or liquidcomponent which is present in a gel or related material, such as water,is replaced first with a mutual solvent for oil and water and finallythe mutual solvent is replaced, directly or indirectly, by a lubricatingoil. Greases of this type have some very desirable properties. Theyappear to have certain advantages over soap thickened greases ofconventional type, some of them being especially suited for hightemperature service. However, as also pointed out in the aforesaidapplications, these greases commonly have the disadvantage that watertends to replace the oil upon contact, causing the composition to breakdown when moisture gains access to the lubricant.

During the course of experiments relating to the present invention ithas been found that the oil thickeners useful for grease making musthave certain physical properties. Conventional colloidal suspensions ofgrease forming particles, such as the soaps of prior art lubricatinggreases, usually must have a high ratio of length to breadth if they areto be useful. In other words, the soap fibres which form in alubricating grease for giving it structural stability are relativelylong, slender and essentially fibrous in character.

Various materials other than soaps have been found in the prior art tohave gel forming characteristics, with lubricating oil. In general,however, the shape of the particles, as well as their size, has animportant bearing upon the character and stability of the lubricatinggrease. It appears that the solid phase of a lubricating grease shouldnot only be fibrous, and its particles relatively long and slender, butit should also possess a strong affinity for oil so that it will attractand hold the lubricating oil to its surfaces to give the greasestructural stability. Patent No. 2,583,603, mentioned above, points outhow various materials much unlike conventional soaps, such as wood puland other cellulose sub- 2 stances may be divided into micro-particlessufficiently fine that a good grease structure may be established whenthey are placed in oil.

It is therefore an object of the present invention to prepare stablelubricating greases from, cellulose and cellulose type materials whileat the same time avoiding the objectionable instability of such greasesin the presence of moisture. According to the present invention, theaddition of certain resins and/or metal soaps to the cellulose materialstends to render them relatively water repellant. Such treatment of thecellulose material is an important feature of the present invention.

When the normal water content of cellulose is replaced by acetone, forexample, and the acetone ultimately replaced by mixing with alubricating oil such as mineral base oil, and then flashing off theacetone, the cellulose retains its original colloidal or gel likestructure unless and until it comes in contact with moisture. Thelubricant is relatively useless in the presence of moisture, however,without additional treatment. By treating the cellulose, while in thepresence of oil, with surface active agents which are hydrophobic innature, the greases are very substantially improved. Various materialswhich reduce substantially the preferential adsorption of water oncellulose and which are sufficiently oleophilic to be wetted by oil maybe employed to accomplish the desired result. The oil soluble waterinsoluble resins and soaps are preferred.

A particularly suitable surface active agent is the resinous reaction'product of substantially equimolar proportions of maleic anhydride andglyceryl monoricinoleate. Other resins of similar type may be used.

A further feature of the present invention involves the treatment of thecellulose itself to give it the desired physical properties forpreparation of lubricating greases. Cellulose of appropriate type may bereadily obtained by treating viscose with dilute mineral acids such, assulfuric acid or phosphoric acid. The sulfuric acid treatment isnormally preferred. By carrying out the acid precipitation in thepresence of sodium sulfate cellulose is produced of sufliciently finefibrous structure that it sets up a stable grease structure withlubricating oils. On the other hand if the cellulose is precipitatedwithout treatment with sodium sulfate the fibrous structure of theprecipitated cellulose is somewhat coarser and less satisfactory.

Although the resinous reaction product of maleic anhydride and glycerylmonoricinoleate is a 3 preferred surface active agent, to render thegrease water repellant and physically stable, other types of surfaceactive agents may be used. In particular, the relatively oil soluble andwater insoluble long chain fatty acid soaps of certain metals may beused to treat the cellulose before oil is incorporated therein. Ingeneral, these metal soaps which make'good grease thickening agents butwhich are substantially insoluble in water, such as aluminum, calcium,barium, or lithium stearate and related materials are useful. It ispreferred that they be used in proportions of about 3 to 60% by weightbased on the weight of solvent exchanged cellulose treated therewith,

or about one-tenth of these quantities based onthe total grease. It ispreferred, however, to use at least some resin of the type mentionedabove, using soap along with the resin where the' 's'o'ap can otherwisebe tolerated. Thus a composition containing about 4 to 10% by weight ofcellulose, based on the solvent-free material, about 4 to 8% of themaleic anhydride glyceryl monoricinoleate resin, jtb6 of soap, andtheremainder of lubricating'oil, preferably but not necessarily ofmmeral'base, makes a good-"grease"composition. Cellulosewhich has notbeen treated with soap atall can be'used." s

hen soap treated cellulose is to be used, the soap ispreferably'formedon the cellulose as the latter is 'precipitated.""either case, upon precipitatioma 'slurry of, viscose is formed whichmaybe treated next with a'inild alkaline solution to condition "it forfurther processing. Thereafterthe slurry is' filtered' andtheprecipitated cellulose is washed substantiallyfree from water solublemamas; It is next solvent exchanged with-a soluble mutual solvent foroil andwaterl 'siich as acetone-"Other mutual sol- Vents, such asan-appropriate alcohol or ether, especially propyl and butyl alcohols,and pyridine, may be-used in lieuof acetone, some of these being pointedoutin Patent No. 2,583,603 pre -reuse mentioned. The solvent selectedshould vaporiz'eat a temperature well below that of the inineral baseoil or other lubricating oil "used. "The mutual solvent may, in "turn,be

replaced directly bylubricatingoiI or 'it' may first be replacedby anintermediate solvent such aspetroleum ether" or the likeandthe'1atter'replaced bythe lubricating oil. Inthis wayjthe watcher-thecellulose-water system may be re-- moved without; shrinkage of thecellulose. cellulose solvent system thus obtained may be termed asolvent-exchangedcellulose; Greases made-directly from thistype'ofcellulose, i. e. by

solvent-exchange, result when oil isadded to" the'solveht 'exchangedcellulose and the solvent is flashed ofi, They immediately begin-todisintegrate," however, in the "presence of water. The cellulosecomponent absorbs or adsorbswa te'r'in preference'to 011* and theproduct is useless, especially-where the grease is to'come incontactwith free water or with appreciable quantities of moisture in'anyform.

The greases of this invention may be substantially improved'in'waterresistance by adding modified resinous condensation products of polyhydric'alc'o'hol and p'olyba'sicacid; These may be waterproofing agentsof the maleate-glycer'yl ester type, previously mentioned.- The mannerinwhich thisis done is an important aspect of this invention. "While,aspreviously mentioned;

the preferred waterproofing agent isthe reaction product of maleicanhydride and glycer'yl monoricinoleate insubstantially equi-mo'larproportions, related alkyd resins such as those obtained by reactingtetrachlorophthalic anhydride with glycerylmonostearate or by reactingsuccinic acid with glyceryl monostearate may be used, though somewhatless satisfactory. Related monoesters of glycerol, such as themono-oleate or monoricihole'ate'i'may bu'sed. l 7

In order "to test water repellancy of various grease samples anapparatus was devised consisting of an elongated grease worker of 50 cc.capacity fitted with a single orifice of diametrl For this test about 10grams of the grease and 40 cc. of water are placed in the worker andforced back andl'fo'rth through the orifice. Thistestordiharily-iscarried out for 50 cycles, passing the greaseand water100 times through the orifice. Greases which do not liquefy ordisintegrate durin'g-such tests are considered to be satisfactorilywater repellant. Some of the products ran considerably more than 50cycles which is considered very superior performance. A typicalexperiment for obtaining a cellulose in sufficiently finely-dividedformfrom viscose consisted in dilutirigfifib' grains of viscose with-I500cc. ofwater containmg 20 gramsfof sodium sulfate. The cellulose w s;then precipitated from the solution withthecal' culated amount'ofsulfuridacidj dilutedwith water 'to"a"volur'ne of 500" cc. This pro'ductwas washed free of water-soluble salts and solvent exchanged withacetone and the acetone "re placed with oil to make a grease m themanner described above. Somc' samples-were tes ted withoutaddition ofwaterproofing or surfaceac tive' agents. In others" the" maleicanhydride glyceryl monoricinoleate" resin was added shown in theexamples below. In" each case-fth'e" oil-cellulose system was"homogenized 1 to make a grease structure." l

' Example} 6.75% by weight of cellulose based on the weight of the finalgrease'was' 'solveritexchanged' firstwith acetone'theh with lubricatingoil er 30Q' viscosity Sz'S. U. at F. The 'oil hada vis-" cosity' indexof 95. 93.25% by weight of'oil with the cellulose made agrease ofgood'yield value uponhomogenization. The product," however}disintegrated without shearing-in the prese'h'ceof water.

Example II 5.5% by weight of solvent exchanged cellulose, based on theweight of th'efinal grease composition, prepared'as described above, wascombined with 5185 of the resin'derived by reacting to completionsubstantially edui molar proportions of 'maleic"anhydride and glycerolmonoricirloleate. "I'othis was added 83.65% ofthe same mineral oil as inExample II" The resulting grease product had'a good consistency andpassed the water "resistance'test of SOs't'rokes of'the plunger in thegrease worker test apparatus described wow,

' Example III 50 strokes of'the mngerer the test apparatus? I suggestedabove, the useof a soap in com bin'a-tion with the resinhas' been'" f unto be" 500 grams of viscose were added to 1500 cc. of water containing20 grams of sodium sulfate and 8.2 grams of sodium stearate. In order tokee the viscosity low the mixture was heated moderately to a temperatureof 50 to 60v C. The cellulose and an aluminum stearate werecoprecipitated from the solution by adding 500 cc.

of an aqueous solution containing the calculated amount of concentratedsulfuric acid and aluminum sulfate. The aluminum sulfate obviouslyreacts by double decomposition with the sodium stearate to precipitatethe aluminum soap. However, since the viscose is normally sufiicientlyalkaline, stearic acid may be used if desired in lieu of sodiumstearate, e. g. as an emulsion in the first water solution mentionedabove.

After precipitation, the slurry of cellulose and soap in water wastreated with to cc. of 3 normal ammonium hydroxide. This raised the pHvalue of the slurry to about 8. The slurry was then filtered, washedfree from soluble salts and solvent exchanged with acetone. and theacetone flashed off by heating above its boiling point.

Greases made in the manner just described were found to be somewhatwater repellant without the addition of resin. However, theydisintegrated after shearing in the presence of water at 70 C., and afew strokes in the grease worker described above.

Example V Example VI A grease was prepared as in Example V except thatthe cellulose contained 10% of its own weight of aluminum mono-stearate.The cellulose and aluminum soap constituted 7.9% by weight, withwaterproofing resin 5.4%, and mineral oil of 90 viscosity index and 500S. S. U. viscosity at 300 F., constituted 86.7%. This product had a goodyield value and passed the water resistance test of 150 cycles. It wasan excellent grease.

Example VII A cellulose prepared as in Example IV but containing 3% ofits own weight of aluminum monostearate coprecipitated therewith wasused in proportions of 8.69% by weight, based on the final grease. 5.21%by Weight of resin and 86.1%

Oil was added 6 of the same oil as in Example VI were blended together.After flashing off the solvent and homogenizing the product in a colloidmill this grease had a good yield value. It passed the water resistancetest of 55 cycles of the plunger but emulsified after 60 cycles. Thisappears to' indicate that it is desirable to have a minimum of at least3% of the soap in the cellulose and preferably a little more.

Example VIII 8% by weight, based on the final grease composition, ofsoap coated cellulose, (coprecipitated with 60% of its own weight ofaluminum monostearate) was prepared as in Example IV. The

cellulose was combined with 6% by weight of the resin of Example II and86% by Weight of mineral lubricating oil of viscosity index and 300 S.S. U. viscosity at F. After heating to C. to flash off the solvent,which was used to displace water from the cellulose, the product waspassed twice through a colloid mill. The resulting grease was found topossess a very good yield value. It had a very firm consistency,considering the amount of thickener employed. This product also passedthe water resistance test of cycles of the plunger.

Instead of the particular maleic anhydridefatty acid resin describedabove, other resins, particularly the commercially available alkydresins 1. A lubricating grease composition compris ing a lubricating oilthickened to a grease consistency with solvent-exchanged celluloseprecipitated from viscose and containing 3 to 60% by weight, based onthe cellulose, of a water insoluble metal soap as a waterproofing agent,said grease containing 2 to 10% by weight, based on the weight of thetotal composition, of a waterproofing alkyd resin of the glycerylpartial ester dibasic acid type.

2. A lubricating grease composition comprising a major proportion ofmineral base lubricating oil, 2 to 10% by weight, based on the totalgrease composition, of solvent exchanged cellulose of gel typeprecipitated from viscose containing 3 to 60% of its own weight of analuminum monostearate as a hydrophobic agent, and 2 to'10% by weight,based on the total composition of a maleic anhydride-glycerylmonoricinoleate ester resin as a waterproofing agent.

3. Composition according to claim 2 where the amount of resin is between5 and 8%.

4. Composition according to claim 2 wherein the amount of cellulose isbetween 5 and 8% of the weight of the total composition.

5. The process of preparing a lubricating grease which comprisescoprecipitating a cellulose of gel type from viscose with a metal soapcapable of rendering the cellulose relatively hydrophobic, addinglubricating oil by solvent exchange to replace the normal water contentof the cellulose, incorporating 2 to 10% by weight, based on the totalgrease composition, of a waterproof- 77,-, c e i an s mc cni in te m. asta e: sytiucfium W t s h ch com ae e n a water. slurry: of viscose"containing mine? 'quan titles, of sodium sulfate and water sol'uhleCizto C20 fatty. acid radical, cobrecipitatingl the celh'ilose and thefatty acid, ragical iromfs'aie' solunanny addition of an" aqgeagsseiiipiof a mineral acid and a mansmtm relat'iy low molecular weight, treatingthe coprecipitate'd slurry with a small-amount'of alkaline material,lter ashi ree fmm watcn solublematerials, exchanging, the water, contentof the filtered; cellulose with a. mutual solvent for water and oil,replacingthe mutualtsolvent with lubricating oil, 'adding2 toil-02 27 byweight, based:

on the.total compositionof awatei'pi oofing resin, and homogenizing toform a stable lubricating. grease.

of; amea p n i 1% h m a y c d. either C12 to Q2 range said. soapbeingselecte 1911 the group consisting of the soap of aluminum, ar m a1m s h droph biq agent.

q s o d ng]: to c aim; herei he resin; is a malei nh d de; x er l mono:ricinoleate reaction product.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,260,625 Kistler Oct. 28 1941 2,573,650 Peterson Oct, 30,1951' 2,583,605 Sirianni et a1 Jan. 29, 1952

1. A LUBRICATING GREASE COMPOSITION COMPRISING A LUBRICATING OILTHICKENED TO A GREASE CONSISTENCY WITH SOLVENT-EXCHANGED CELLULOSEPRECIPITATED FROM VISCOSE AND CONTAINING 3 TO 60% BY WIEIGHT, BASED ONTHE CELLULOSE, OF A WATER INSOLUBLE METAL SOAP AS A WATERPROOFING AGENT,SAID GREASE CONTAINING 2 TO 10% BY WEIGHT, BASED ON THE WEIGTH OF THETOTAL COMPOSITION, OF A WATERPROOFING ALKYD RESIN OF THE GLYCERYLPARTIAL ESTER DIBASIC ACID TYPE.